Electric Flywheel

[DCB]

Perhaps the answer is to have an on board battery for power and use the rails to carry only the control signals...

[AndyID]

Perhaps the answer is to have an on board battery for power and use the rails to carry only the control signals...

I understand there is a lot of effort going into that area. Some methods use radio for control and rail power to charge the batteries, and it's only necessary to feed power to some bits of the track. Battery size is still something of an issue, particularly with smaller scales and small outline locomotives. I'm sure some of the people who have posted here have a much better understanding of the "state-of-the-art" than I do.

[Dagworth]

This was thread that solved the problem of DC keep alive about a year ago. IIRC, it had a relay and a battery and reference cap that locked onto to the driving voltage if the power cut out. I'll check my history.

 

Andy

See reply number 15 of this thread

 

Andi

[AndyID]

In terms of energy density it looks like a supercap wins.

 

Assuming I didn't mess up the calculations:

 

A 1 farad supercap charged to 3 volts stores 4.5 joules.

 

A solid brass flywheel diameter 15.24 mm 13.97 mm long spinning at 10,000 RPM stores 0.34 joules.

[Gordon H]

In terms of energy density it looks like a supercap wins.

 

Assuming I didn't mess up the calculations:

 

A 1 farad supercap charged to 3 volts stores 4.5 joules.

 

A solid brass flywheel diameter 15.24 mm 13.97 mm long spinning at 10,000 RPM stores 0.34 joules.

Also bear in mind that for a DC arrangement you would likely use four of these in series to give a 12V 0.25F storage capacitor, so 18 Joules.

[AndyID]

Also bear in mind that for a DC arrangement you would likely use four of these in series to give a 12V 0.25F storage capacitor, so 18 Joules.

I'm not sure I'd want to do that, not in OO anyway. The caps are not all that small. I think that takes us back to the need for a DC-DC converter to convert the cap output into a higher voltage (which seems to be what the DCC systems do).

 

By the time we get to that point I'm inclined to think it might be better to "bite the bullet" and replace the cap with a lithium-ion battery. It's probably about the same amount of electronics either way.

[96701]

I have a Hornby class 50 fitted with a decoder (can't remember what type) that I inadvertently ran on Geoff Brewin's dc layout that was controlled via the MERG Superbloc system. The system had a couple of rail breaks in each block, so if the block in front was occupied, the dc voltage was gently reduced from the first rail break and more quickly reduced after the second rail break to bring a dc loco to a stand in more or less the right place.

 

The class 50 with the decoder in behaved somewhat alarmingly different in that it didn't slow down as quickly, so would sometimes overrun the last rail break and run into the next section that already was running at max voltage because there was a train in section.

 

There was so much mayhem ensuing that the loco was banished from Geoff's layout, however it was a good example of 'electronic flywheel' for very little effort or expense.

[Pacific231G]

This is just about an idea had and experimented with a bit. Be warned; it was not a great success, but it was interesting. Maybe someone can make something of it. It's probably not a new idea either.

 

As we all know, poor contact between the rails and a locomotive motor "can lead to disappointment" (or much worse). It's well known that one of the ways minimize this problem is with a flywheel on the motor. Flywheels help, but they tend to help more at high speed when you are less likely to need them. Also, it can be difficult to find room for them, and if they are not well balanced, they can accelerate the wear on motor bearings.

 

A much better solution might be an electronic energy storage device that can maintain power to the motor during temporary "rail-power" interruptions. A capacitor might be just the thing, but unfortunately, there don't seem to be any that are suitable. It would almost certainly be an electrolytic capacitor, but that means it only works in one polarity, and DC motors have to operate in either polarity. The same issue applies to batteries.

 

What we need is an electronic storage device that can store a lot of energy, does not take up a lot of space and is happy to operate on either polarity.

 

Sounds a lot like a motor with a flywheel. When the power is cut to the motor, the flywheel drives the motor and the motor acts as a dynamo. So, the idea is to put a free-running motor with a flywheel in parallel with the motor that is geared to the wheels.

 

I tried it, and it does work, but not as well as I had hoped. I didn't really spend a lot of time on it, so there may be hope. I think one problem might be the voltage drop across the carbon brushes which prevents the storage motor from supplying the same voltage that "charged" it.

I think the first person to use, or at least to write about, this idea was the late Bob Symes. It was AFAIR in an article in MRC titled "free motors"  and it was applied to the power car of a DMU which had plenty of space for the second motor and flywheel. ISTR that the idea wasn't so much to overcome dead spots in the track as to recreate the different (from a steam loco) characteristic movement of a diesel unit particularly as it pulled away.